Many important drugs have limited solubility in water, especially hydrophobic or lipophilic agents. In order to attain the full expected therapeutic effect of such agents, it is usually required that a solubilized form of the drug be administered to a patient. The poor water-solubility of these lipophilic agents often results in major difficulties in formulation, particularly when easily sterilizable and administrable homogeneous aqueous solutions are needed. Efficacious aqueous-based formulations are particularly problematic for systemic administration, in particular parenteral administration (i.e., injectable solutions) and for certain liquid preparations for, e.g., topical gynecologic, dermatologic ophthalmic, etc. use, and for use on the oral mucous membranes.
A number of methods for solubilizing drugs have been developed and most of them are based on the use of solvents or cosolvents, surfactants, complexing agents (for example, cyclodextrins or nicotinamide), or use of complicated drug carriers (for example, liposomes). Each of the above methods has one or more particular drawbacks. For example, the use of conventional surfactants and cyclodextrins to solubilize hydrophobic drugs has drawbacks related to surfactant and cyclodextrin toxicity and/or precipitation of the solubilized drugs once administered to the patient or when otherwise diluted in an aqueous environment. For therapeutic drugs that cannot be formulated as an aqueous solution, emulsions have oftentimes provided a cost-effective and therapeutically acceptable alternative. However, it is difficult to render emulsions sterile and/or endotoxin free for intravenous injection, and terminal sterilization by heat or filtration treatments is not suitable for all emulsions.
Disclosed herein methods to improve the solubility of therapeutic agents, preferably lipophilic agents, in mixtures comprising C60 fullerene and lipophilic solutions.